Metabolic Fate of Peanut Skin A-Type Proanthocyanidins and Their Effects on Endogenous Metabolites in Mice

Peanut skins are rich in A-type proanthocyanidins (PACs); However, their in vivo metabolic fate remains poorly understood. In this study, the composition of peanut skin proanthocyanidins (PSP) was characterized, followed by a comparative investigation of the metabolic fate of PSP and catechin and their effects on endogenous metabolites in mice. The results showed that PSP contained 51 PACs and flavan-3-ols, with a purity of 69.51% and an average degree of polymerization (DP) of 2.59. Metabolomic analysis revealed that PSP exhibited lower bioavailability, as well as lower conversion efficiency into characteristic phenyl-γ-valerolactone metabolites compared with catechin. However, PSP and catechin showed similar conversion efficiencies into common microbiota-derived phenolic metabolites, including 3-(3′,4′-dihydroxyphenyl)propionic acid, 3-(3′-hydroxyphenyl)propionic acid, and 3′-hydroxyphenylacetic acid. Additionally, catechin as well as A-type procyanidin dimers and trimers underwent C-ring opening, but only catechin-derived products entered systemic circulation. PSP and catechin exhibited similar effects on endogenous metabolites and metabolic pathways, both altering fecal bile acids, phospholipids, lysophospholipids, and pathways related to aromatic amino acid metabolism, pentose and glucuronic acid metabolism, and the tricarboxylic acid cycle. These results reveal both metabolic convergence and structure-dependent specificity in PAC biotransformation, suggesting that shared gut microbial metabolites may underlie common physiological effects, while differences in polymerization degree and molecular structure shape absorption, circulation, and host–microbiota metabolic interactions, with implications for precision nutrition strategies.